Method of pot life extension for polyurethane propellants



April 18, 1967 E. J. WALDEN ETAL 3,314,834

METHOD OF POT LIFE EXTENSION FOR POLYURETHANE PROPELLANTS Filed Dec. 14, 1962 5 Sheets-Sheet 1 VISCOSITY TIME (FROM ISOCYANATE ADDITION), HOURS PIE 1.

VISCOSITY s2o,0o0

|00,000 COMPOSITION A WITH m 1,3-DIPHENYL-1.3-PROPANEDIONE (DEM) E1 2,4-PENTANEDIONE 8OOOO A l-PHENYL-l,3-BUTANEDIONE v 4,4,4-TRIFLUORO-1(2-THlENYL)- 1,3-BUTANEDIONE 60,000 0 BLANK TIME (FROM ISOCYANATE ADDITION), HOURS INVENTORS JACK K. WEST BY ERNEST J. WALDEN WMM ATTORNEYS April 18, 1967 E, w D N A 3,314,834

METHOD OF POT LIFE EXTENSION FOR POLYURETHANE PROPELLANTS Filed Dec. 14, 1962 3 Sheets-Sheet 2 COMPOSITION B WITH Ia kSIi/ISHENYb1,3-PROPANEDIONE VlSCOSlTY El 2,4- PENTANEDIONE A 1- PHENYL-1,3- BUTANEDIONE 0 TRANS-1,4DlFHENYL-2BUTENE- I,4 DIONE BLANK TIME (FROM ISOCYANATE ADDITIONLHOURS COMPOSITION 0 WITH:

1,3-DlPHENYL-1,3-PROPANEDIONE (DBM) 2,4 PENTANEDIONE I-PHENYL-LB-BUTANEDIONE 4,4,4-TRIFLu0R0-I (2-THIENYL)-1,3-BUTANEDIONE TRANS-I,4-DIPHENYL2BUTENE-1,4 DIONE BLANK VISCOSITY INVENTORS TIME (FROM ISOCYANATE ADDITION), HOURS JACK K WEST ERNEST J. WALDEN BY ATTORNEYS VISCOSIT April 18, 1967 E. J. WALDEN ETAL 3,314,834

METHOD OF POT LIFE EXTENSION FOR POLYURETHANE PROPELLANTS Filed Dec. 14, 1962 5 Sheets-Sheet 3 COMPOSITION D WITH:

'CUO O Q3 CUO O AND 2,4-PENTANED|ONE l3 2,4-PENTANEDIONE 80.000 BLANK o o e:

o 8 I6 24 32 40 4s 56 64 72 TIME (FROM ISOCYANATE ADDITION), HOURS INVENTORS JACK K. WEST BY ERNEST J. WALDEN ATTORNEYS United States Patent Oil 3,314,834 METHOD OF POT LIFE EXTENSION FOR POLYURETHANE PROPELLANTS Ernest J. Walden, Mountain View, and Jack K. West, Palo Alto, Calif, assignors to United Aircraft Corporation, a corporation of Delaware Filed Dec. 14, 1962, Ser. No. 244,753 7 Claims. (Cl. 149-19) increases the cure time unduly and frequently results in a soft or incomplete cure.

In the drawings forming a part of this application:

FIGURES 1-5 are graphs showing the effect of various additives on pot life extension.

In accordance with the present invention, it has been found that diketo compounds form effective pot life extension agents in polyurethane propellants, permitting the In one typical propellant system, when the burning rate catalyst was omitted, the system had a pot life of approximately four hours at 75 F. As used herein, pot life is defined as the time required for the viscosity to reach 2 0,000 poise when measured by a Brookfield viscometer with a helipath stand and a TF spindle rotating at 0.5 r.p.m. When 1% of a burning rate catalyst was added, the pot life was reduced to less than /2 hour. However, by the employment of 0.04% dibenzoyl methane, pot life was extended to over five hours.

This invention is not based on any theory of its operation but it is believed that the diketo compound acts as the normal curing tempera- 3,314,834 Patented Apr. 18, 1967 ice Typical non-limiting examples of the compounds which can be used are:

2,4-pentanedione 1-phenyl-1,3'-butanedione 4,4,4-trifluoro-1 (Z-thienyl) -1,3-butanedione Trans-1,4-diphenyl-2-butenel,4-dione 1,3-diphenyl-1,3-propanedione (also called dibenzoylmethane).

Of these compounds, dibenzoylmethane is preferred because of its high effectiveness, lower cost, and ready availability.

The quantity of the diketo compound which is utilized is quite small and Polypropylene glycol (Dow P-2000, diol)- Polyoxybutylene (Dupont LD-124, diol) Polypropylipe adduct of glyeerine (Dow -8 trio Triethanolamine Hexamethylene diisocyanate 3,3-dimethyldipheny1metl1ane-4-4- diisocyanate (Dupont Hylene DMM) 2 ,golylene diisocyanate (Dupont Hylene Aluminum powder Ammonium perchlorate.-. Lecithin (Yelkins TTS) Sulfur Ferric acetylacetonate (cure catalyst) Dibutyl tin dilaurate (cure catalyst) opper chromite burning rate catalyst Silicon dioxide (Cabosil, filler) rise above 20,000 poises.

To further illustrate the invention, the compositions set forth in the I) pound appreciably extended the pot life of the polyurethane propellant mixture.

In composition D and the graph of FIGURE 5, dibutyl tin laurate was substituted for the ferric acetylacetonate of the other compositions. Also, comparisons were made with and without 1% of copper chromite and with and without 0.12% by weight of 2,4-pentanedione. It will be seen that the dibenzoyl compound greatly extended the pot life both with and without the presence of the burning rate catalyst.

We claim:

1. In the process of making a polyurethane propellant wherein a diisocyanate is polymerized with a polyhydroxy organic compound in the presence of a curing rate catalyst, the improvement comprising: adding to the composition a diketo compound of the formula \l H R\CR2-C-R; wherein R and R are alkyl, haloalkyl and aromatic radicals and R is selected from the group consisting of lower alkylene and lower alkenyl radicals.

2. The method of claim 1 wherein the composition 4 contains a cure catalyst selected from the group consisting of dibutyl tin laurate and ferric acetylacetonate and wherein the amount of the diketo compound is about 3 times the weight of the cure catalyst.

3. The composition of claim 1 wherein the diketo compound is 2,4-pentanedione.

4. The composition of claim 1 wherein the diketo compound is 1-phenyl-1,3-butanedione.

5. The composition of claim 1 wherein the diketo compound is 4,4,4-trifiu0ro-1(Z-thienyl)-1,3-butanedione.

6. The composition of claim 1 wherein the diketo compound is trans-1,4-diphenyl-2-butene-l,4-dione.

7. The composition of claim 1 wherein the diketo compound is 1,3-dipheny1-1,3-propanedione.

References Cited by the Examiner FOREIGN PATENTS 1,291,647 3/ 1962 France.

CARL D. QUARFORTH, Primary Examiner. L. A. SEBASTIAN, Assistant Examiner. 

1. IN THE PROCESS OF MAKING A POLYURETHANE PROPELLANT WHEREIN A DIICYANATE IS POLYMERIZED WTH A POLYHYDROXY ORGANIC COMPOUND IN THE PRESENCE OF A CURING RATE CATALYST, THE IMPROVEMENT COMPRISING: ADDING TO THE COMPOSITION A DIKETO COMPOUND OF THE FORMULA 